I don't know anything about novels about autism. But I do wonder about the character Friendly in Best Served Cold by Joe Abercrombie.
Friendly finds it impossible to relate to other people regarding their wants and needs. They don't really seem to relate to his interests. He finds solace in counting. He counts everything. He like it when the numbers come out the same every day. (The same number of bricks on the steps. The same number of buttons on his shirt. The same number of guards at the prison.) Friendly serves time in prison and actually feels connected to the guards... because they count out loud. And furthermore, they count him. He likes to be counted. Their vocal counting reassures him.
In prison, Friendly becomes attached to a loan shark. In his eyes, the loan shark tries to make the numbers come out correct while the borrowers have problems making the numbers correct. Since Friendly likes to make the numbers always come out correct, he becomes the loan sharks' collector. And it just so happens that Friendly is good with his fists... and a knife.
Friendly's thought processes are interesting. Walking, resting, eating, working, fighting... he's always counting... and making connections through numbers. This is very handy since he's on a mission to kill six men. Five left. Four... three... two... one...